This invention relates to means for interlocking adjacent components of rotating assemblies to prevent relative rotation between them. The invention is especially, but not exclusively, applicable to devices for interlocking rotary components of gas turbine engines.
In the construction of turbines for gas turbine engines, a circumferential array of radially-extending turbine blades are mounted on the periphery of a turbine disc by engagement of fir tree or other formations at the blade roots with complementary formations formed around the periphery of the disc. Axial movement of the blades relative to the disc is prevented by annular end or seal plates which locate over the interengaged formations and also act as a seal between cooling air flowing through the fir tree formations to the interior of the turbine blades and combustion gases flowing around the turbine blades.
Typically such seal plates are secured in place by means of cooperating radially extending projections and lugs spaced apart around the respective components and arranged such that during assembly the seal plate may be moved axially into engagement with the rotor disc and then rotated to bring the projections and lugs into positions in which they interfere with one another and retain the seal plate in engagement with the disc. Components interconnected in this manner are referred to herein and in the appended claims as xe2x80x9crotationally interengaged componentsxe2x80x9d.
Once engaged, the rotor disc and seal plate are locked against relative rotation by means of at least one locking device adapted to be inserted into one of the gaps between adjacent interengaged projections and lugs, the locking device being operable to prevent relative rotation of the disc and seal plate and thus retain the projections and lugs in their interengaged positions. The or each locking device is retained in position by a retaining member adapted to be deformed around a portion of the seal plate.
Previously proposed locking devices for this purpose have suffered from a number of disadvantages. In particular they have required complex machining operations during production and are prone to fretting corrosion and cracking resulting from stresses generated during engine operation.
According to one aspect of the present invention there is provided a locking device for use in retaining rotationally interengaged components in engagement with one another, the device comprising a body member adapted to be located between adjacent interengaging formations on the components in a manner to prevent relative rotation of the components, and a retaining member adapted to locate the body member in position, the retaining member being formed from wire and comprising at least two hook-like members engaged in spaced apertures in said body member, each hook-like member having first and second portions thereof extending beyond said body member into engagement with inner and outer surfaces of one of said components.
Preferably the components comprise a rotor disc and seal plate of a turbine assembly, said portions of said retaining member extending radially outwardly of said body member into engagement with adjacent inner and outer surfaces of said seal plate.
Thus the invention also provides a locking device for retaining a rotationally interengaged seal plate and rotor disc of a gas turbine engine in engagement with one another, the device comprising a body member shaped and dimensioned to form a close fit within a gap between adjacent interengaged lugs and projections on the seal plate and rotor disc, and a retaining member formed from wire and comprising at least two hook-like members engaged in spaced apertures in said body member, each hook-like member having first and second portions extending beyond said body member into engagement with inner and outer surfaces of said seal plate.
Preferably the spacing between said hook-like members differs slightly from the spacing between said apertures in the body member, whereby the retaining member is maintained under tension or compression.
Preferably the retaining member is formed by bending from a single length of wire. Preferably said wire and said apertures are of circular cross-section and of substantially the same diameter, whereby the hook-like members are a close fit in the associated apertures.
Preferably also the opposite ends of the apertures in said body member are of tapered, chamfered or other outwardly increasing cross-section whereby to maximise surface contact between the walls of the aperture and the wire.
The invention also comprises a turbine rotor assembly for a gas turbine engine incorporating a locking device according to the preceding paragraphs.
Thus the invention further provides a turbine rotor assembly for a gas turbine engine comprising a rotor disc having a plurality of blades secured at the periphery thereof, an annular seal plate engageable with said disc to retain said blades against axial movement relative to the disc, means for releasably securing the seal plate to the disc in abutting relationship, said means including circumferentially spaced cooperating formations in the form of projections and recesses on the seal plate and the disc adapted for axial engagement and relative circumferential movement to secure the seal plate to the disc, and a locking device to lock the seal plate and disc against relative rotational movement, the locking device comprising a body member engageable in a gap between adjacent interengaged formations and a retaining member formed by bending from a single length of wire to form a pair of side-by-side hook-like elements each adapted to pass through an associated aperture in said body member and having inner and outer portions thereof extending beyond said body member into engagement with inner and outer surfaces of said seal plate to retain the body member in position in said gap.